In the growing of row crops, it is known that it is advantageous to loosen the compaction of the soil to a considerable depth prior to planting the seeds by running a sub-soiler along the centerline of each proposed crop row. Such deep cultivation allows deeper root growth of the plants, and leads to greater yields. In the interest of efficiency, such sub-soilers have been used as part of a combination implement, mounted to run immediately prior to a planter of the type generally known to those skilled in the art.
A problem that arises in using such a combination implement results from the fact that a sub-soiler leaves a deep groove or furrow that is not generally sufficiently filled in by the natural resettling of the soil behind the sub-soiler. Seeds dropped by the planter may fall too deeply into this furrow, especially if planting is followed closely by a rain, which may wash the seeds deeper into the furrow. If the seeds are planted too deeply, the young plants are not able to emerge. Attempts have been made in the prior art to include implements between the sub-soiler and the planter to prepare the seed bed. One common method has been to mount rotary spiders at the sides of the sub-soiler furrow to throw dirt from off the row into the furrow to fill it in. However, it has been found that the dry dirt thrown into the furrow provides a poor environment for the germination of the seed. Consequently, the desired density of plants along the row is difficult to control, a substantial amount of seed can be wasted, and gaps along the rows may lead to lower yields.
A means for leveling furrows left by a series of chisel plows is disclosed in U.S. Pat. No. 3,692,120. The device therein disclosed includes a rotary tool having fixed horizontal blades extending transverse to the row for pulverizing the soil, and a leveling blade following behind the rotary tool. Although operation of such an implement could result in filling in the furrows left by the chisel plows, it would leave a flat, level surface, whereas many farmers prefer to plant in a slight depression so that the depression can be filled with dirt to cover small weeds when the plants are at an early stage of growth.
Thus, there has been a need in the art for a seed bed preparation tool that could be run between a sub-soiler and a planter, and that would be capable of filling in the sub-soiler furrow with moist dirt turned up by the sub-soiler and also capable of preparing a suitable seed bed in a slight depression.